Asphalt pavements, besides being subject to corrosion by sun and rain, as well as to deterioration and disintegration from two other sources, namely, from the chemical action of oils, greases, and other petroleum products, and from mechanical action such as is produced by contact of the wheels of vehicles and other objects in passing over surfaces of such pavements.
Heat of the sun causes softening of the asphalt surface and, in combination with the oxygen of the atmosphere, produces oxidation of the asphalt, thereby hastening its deterioration. Rain, by seeping into the asphalt surface, impregnates the porous aggregate materials therein with which the asphalt is normally mixed in producing such pavements, thereby also hastening the disintegration of the pavement.
By their chemical action, oils, greases, and other petroleum products, dissolve the asphalt, thereby loosening it from the aggregate with which it is normally mixed. This loosening is hastened by the movement of vehicles thereover and by other mechanical sources to which the pavement is normally subjected.
The size of the particles of the aggregate materials that are mixed with the asphalt in producing a pavement have a pronounced effect on the degree of resistance that the pavement provides against skidding or sliding, which resistance increases with the increase in size and porosity of the particle of the aggregate. The amount of oil, grease, and other liquids that can seep into surface of the pavement also increases with the porosity of the aggregate.
In order to reduce deterioration and disintegration of asphalt pavements from such sources, epoxy resins have been combined with asphalt by melting the two substances together. Although such a mixture reduces to a degree of about 15% the effects of such chemical and mechanical actions, the cost of the pavement is increased about 350%, and the curing of the epoxy resin that is thus combined with the asphalt requires almost 72 hours.
Attempts to improve the resistance of such asphalt pavements to corrosion by applying calcined bauxite over the asphalt surface fails to achieve any desirable results because of the failure of the calcined bauxite adequately to adhere to or combine with the asphalt.